In a well known manner, such an adjustment is intended to vary the length of the side arms in order to adjust to the physiological differences between the people who wear these spectacles. Such an adjustment can also serve to increase the retention of the spectacles on the face of a specific person during certain activities in order to prevent the spectacles from shifting their position on the face or falling off in extreme cases. The invention also relates to this particularly desirable alternative when wanting to participate in athletic activities, for example.
There is a known conventional pair of spectacles of this type in which each side arm comprises a first portion and a second portion that slide relative to one another in a sliding direction, between a retracted position and an extended position.